The events of Sep. 11, 2001 instigated an urgency for more effective and stringent screening of airport baggage. The urgency for security expanded from an inspection of carry-on bags for knives and guns to a complete inspection of checked bags for a range of contraband with particular emphasis upon concealed explosives. X-ray imaging systems including a computed tomography (CT) system are currently employed for screening.
The CT system includes an X-ray source that generates X-rays that pass through a material. The CT system further includes a detector that detects the X-rays to create a plurality of signals. The CT system also includes a computer that generates an image of the material from the signals. However, a resolution of the image may not have a suitable quality to enable identifying the material as a threat material.
Identification systems based on X-ray diffraction (XRD) techniques provide an improved discrimination of the material compared to that provided by the X-ray imaging systems. The XRD identification systems measure d-spacings between lattice planes of micro-crystals in the material. A “d-spacing” is a perpendicular distance between adjacent lattice planes in the material. However, if the XRD identification systems include the detector and the computer mentioned above, the XRD identification systems may generate an image that is not of suitable quality. Accordingly, the diffraction techniques may suffer from a high false alarm rate for some classes of substances.